Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Quantos clubes estavam envolvidos na segunda rodada?
 ###Tabelas: CREATE TABLE the_2011_season (the_2011_season_id AUTO_INCREMENT PRIMARY KEY, Position INT, Driver / Passenger VARCHAR, Equipment VARCHAR, Bike No INT, Points INT) CREATE TABLE models_except_north_america_and_japan (models_except_north_america_and_japan_id AUTO_INCREMENT PRIMARY KEY, Chassis code VARCHAR, Years VARCHAR, Model VARCHAR, Engine VARCHAR, Power VARCHAR, Torque VARCHAR) CREATE TABLE tank_locomotives (tank_locomotives_id AUTO_INCREMENT PRIMARY KEY, Class VARCHAR, Railway number(s) VARCHAR, Quantity INT, Year(s) of manufacture VARCHAR, Type VARCHAR) CREATE TABLE north_dakota_counties_by_per_capita_income (north_dakota_counties_by_per_capita_income_id AUTO_INCREMENT PRIMARY KEY, County VARCHAR, Per capita income VARCHAR, Median household income VARCHAR, Median family income VARCHAR, Population INT, Number of households INT) CREATE TABLE teams (teams_id AUTO_INCREMENT PRIMARY KEY, Round VARCHAR, Clubs remaining INT, Clubs involved INT, Winners from previous round VARCHAR, New entries this round VARCHAR, Leagues entering at this round VARCHAR)  
SELECT Clubs involved FROM teams WHERE Round = Second round